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Compatibility Investigations on Novel Energetic Formulations of Nitrogen Rich Azole
[Bistetrazolylamine(BTA)]
Sasidharan Nimesh*, Pisharath Sreekumar, Zhang Fan and How‐Ghee AngEnergetics Research Institute, Nanyang Technological University, N1‐B4a, 50 Nanyang
To investigate the compatibility of binders with Bistetrazolylamine(BTA), in an effort toassess the applicability of the molecule in explosive and propellant formulations.
BTA represents one of the attractive energetic candidates with high-energy densityand insensitivity, a rare combination.
Although synthesis and characterization of novel high energy-insensitive moleculesare reported, very few have been tested for their compatibility with known binders.
Lack of information on the compatibility and stability of high nitrogen molecules hinderstheir further development as a formulation.
High density CHN molecule. (1.86 g/cc) Symmetrical tetrazolyl groups on the central
nitrogen-high energy system not local minima. Presence of substitution and salt formation changes
the structure to most stable low energy form.
Thermal characterization and P-t studies on BTA
BTA shows excellent thermal stability up to 2400C
DSC curve shows maximum heat release with in a short temperature range.
P-t curve was measured to understand the ignitability and pressure response of BTA.
0 100 200 300 400 500
0
20
40
60
80
100
Wt = 87.5% (decomposition)
Wei
ght L
oss
(%)
Temperature (0C)
Wt = 10.3 % (H2O loss)
100 200 300 400 50020
40
60
80
100
120
140
Hea
t FLo
w (m
W)
Temperature (0C)
Tp = 245.5 0C
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
0.0
0.5
1.0
Pres
sure
(MPa
)
Time (S)
Pmax 1.0 MPatpmax 0.52 S
dp/dt 16.93 MPaS-1
Energetic binders : GAP & PNIMMO
Binder Mol. Weight,Mn, gmol
-1Density, gcc-1
Glass transition, Tg, 0C
Decompositiontemperature, Tp, 0C
Heat of decomposition, Jg-1
GAP 2835 1.35 ‐51.2 241.5 1917
PNIMMO 1295 1.28 ‐55.5 204.6 1123
EC with 48% ethoxy content was procured from Sigma Aldrich and used as received.
Importance of Compatibility studies
Compatibility using micro-calorimetry as per STANAG 4147
Compatibility of novel energetic materials with components of formulations/composites are crucial fortheir safety and functioning. Ideally compatible materials should not have any chemical interaction witheach other over a prolonged period.
STANAG 4147, MIL-STD-268B and MIL-STD-650 explains the various test procedures andcompatibility criteria for energetic materials.VST, IST, TG and DSC analysis includes the various test fordetermining the compatibility.
High degree of accuracy in temperature profile and high sensitivity (nW) of micro-calorimeter isadvantageous to measure heat flow over a long period. 6 channel TAM III from TA was used.
Test measurements:
Degree of compatibility:
Acceptance criteria:
1:1 mixture by weight of : Energetic material (BTA) + sample(binder)
D= 2M/(E+S)
M = Heat generation for the mixture (J g-1)E = Heat generation for energetic material(BTA) (J g-1)S = Heat generation for the sample(binder) (J g-1)
Criteria:D > 3 : Incompatible2 < D < 3 : Another method should be used
Stability and heat flow of BTA and Binders
Thermal decomposition of BTA, GAP and PNIMMO occurs within a closer range of temperature.
PNIMMO showed a faster heat accumulation rate at 850C when compared to the other components
-20 0 20 40 60 80 100 120 140 160 180
-20
0
20
40
60
80
100
Nor
mal
ized
Hea
t (Jg
-1)
Time (h)
BTA GAP EC PNIMMO
0 100 200 300 400
Wei
ght l
oss(
%)
Temperature (0C)
BTAECGAP PNIMMO
Compatibility : BTA-GAP
Compared with the individual components,mixture showed increase in heataccumulation after 60 h
No appreciable heat release rate over 168h.
BTA: -18.9 J/g; GAP -22.6; BTA-GAP: -14.05J/g
D<2
0 20 40 60 80 100 120 140 160 180
-26-24-22-20-18-16-14-12-10-8-6-4-20
Nor
mal
ized
Hea
t (Jg
-1)
Time (h)
BTA GAP BTA-GAP
Compatible mixture
0 20 40 60 80 100 120 140 160 180-0.000016
-0.000014
-0.000012
-0.000010
-0.000008
-0.000006
-0.000004
-0.000002
0.000000
0.000002
Heat Flow Normalized Heat
Time (h)
Hea
t Flo
w (m
W)
-30
-25
-20
-15
-10
-5
0
Nor
mal
ized
Hea
t (Jg
-1)
Compatibility : BTA-PNIMMO
Notably the mixture has lower heat releaserate when compared to PNIMMO